CVE-2026-55011: Microsoft Microsoft Malware Protection Engine

Microsoft Defender Remote Code Execution Vulnerability

CVSS 7.8 HighEPSS 0.0047 · 40th percentile

Published by the CVE Program (CNA: microsoft) at 14 Jul 2026, 17:05 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Microsoft	Microsoft Malware Protection Engine	affected 1.1.0.0 to before 1.1.26060.3008 custom

Identifiers

CVE-2026-55011

CNA

microsoft

Weakness (CWE)

CWE-191

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Microsoft Malware Protection Engine versions 1.1.0.0 before 1.1.26060.3008 contain an integer underflow that allows code execution. The source describes the flaw as allowing an unauthorized attacker to run code locally, but gives few other details. Upgrade to version 1.1.26060.3008 or later.

Written 13 Nov 2026.

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.8	High	3.1	CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C	CNA (microsoft)

CISA KEV Not listed.
EPSS 0.0047, the 40th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

14 Jul 2026, 17:05 UTC Confirmed by the CVE List

Sources

References from the CNA

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55011 vendor-advisorypatch

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.